This application claims priority from Japanese Patent Application Reference No. 11-356970, filed Dec. 16, 1999.
The present invention is related generally to techniques for performing real time backup and copying of data, and specifically to techniques for updating data in the event of an emergency.
Conventional real time remote copy technology provides real time backups of system data in data storage controllers. Backups are prepared and forwarded to a system distant from the system being backed up. The backup data is updated in real time, so that it can be used in order to recover quickly from trouble, such as system faults and the like, for example. Backup data (xe2x80x9csecondary dataxe2x80x9d) is expected to be located as far away from the data (xe2x80x9cprimary dataxe2x80x9d) of a working system (xe2x80x9cprimary systemxe2x80x9d) in order to prevent damage to the secondary data caused by a wide spread disaster such as an earthquake, for example. In order to keep the secondary data to be completely coincident with the primary data after updating the primary data, it is also necessary to proceed to the next step in the primary system processing only after confirming that the secondary data has been updated (xe2x80x9cperform a synchronous remote copyxe2x80x9d).
However, the farther a storage device for storing the secondary data is located, the longer the data transfer time and therefore, the communication time for the confirmation of the completion of updating the secondary data, can become. As a result, the processing performance of the primary system deteriorates with increasing distance.
What is needed are improved techniques for performing data backup.
According to the present invention, techniques for performing real time backup of data in the presence of a pending hazard, such as a natural disaster, or the like, are provided. Embodiments can provide data storage controllers, networked data storage systems, methods and the like, that detect imminent hazardous conditions and alter backup behavior to provide greater integrity of backed up data.
In a representative embodiment according to the present invention, a data storage apparatus is provided. The data storage apparatus can comprise one or more storage media; a cache memory; and a controller. The controller can move data into and out of the storage media and the cache memory. The controller can also receive data from an external source for storage, for example. Further, the data storage apparatus can comprise a hazard sensor. Responsive to the hazard sensor detecting a probable occurrence of a hazardous event, the controller can copy data from the cache memory to the storage media in order to preserve a copy of the data.
In another representative embodiment according to the present invention, update of primary data can be temporarily suspended after the recognition of a probable occurrence of a hazardous event. By suspending updating the primary data temporarily, the presence of un-updated data can be minimized, so that lost data is decreased. Then, the secondary data can be updated quickly or exclusively, in order to avoid inconsistent copies of secondary data.
In a further representative embodiment according to the present invention, an asynchronous copy operation can be temporarily suspended after the recognition of a probable occurrence of a hazardous event, and the copy mode can be changed from the asynchronous copy mode to a synchronous copy mode. Updating of the secondary data can then proceed using a synchronous copy mode so that data loss can be minimized.
In a still further representative embodiment according to the present invention, a link to a remotable storage system can be provided. The controller can copy data over the link to the remotable storage system in order to make a remote backup. A primary disk controller can prioritize the remote copying instead of storing the data into the local non-volatile disk, for example. Specific embodiments that perform such remote copying use the remote system as a backup while the local system is down for some reason. In such case, the remote system can replace the local system. If the local system is damaged by a serious disaster, it is not useful to keep the data at the local site. Thus, in such cases, the primary storage system can prioritize the remote copying with respect to storing data to a local non-volatile disk, for example.
In a still yet further representative embodiment according to the present invention, a data storage controller can prioritize the data storage to a local non-volatile disk. This can be especially useful in installations where the remote copying is used to create the remote data merely as a backup data. In such embodiments, remote copying provides a non-stop data backup, while the backup to the other media such as magnetic tape, for example, requires stopping of the operation of the system. Thus, in case of a serious disaster, it may be important to store the data at the local site (to a non-volatile disk, for example). Another embodiment in which higher priority may be given to local copying are installations where there is a possibility that the remote copying path could also break down. In such installations, it is of little use to copy the data to the remote site. Thus, in such embodiments, storing the data at the local site, to a non-volatile disk, or the like, will be given a higher priority over making a remote copy of the data.
In specific embodiments in which the primary system comprises a plurality of storage controllers, recorded data can be distributed across two or more of the plurality of storage controllers, to storage devices that are connected to each of a plurality of storage controllers, for example. In such embodiments, the present invention provides for maintaining updated copies of data across the plurality of storage controllers. In a specific embodiment, the storage controllers of the primary system can be provided with a common communication line connecting them together. Once interconnected, the storage controllers can coordinate backup copying of data in order to prevent data loss.
Numerous benefits are achieved by way of the present invention over conventional techniques. The present invention can provide real time data backup and copy functions from a primary system to a secondary system switchable between a synchronous and an asynchronous copy mode. Backup may be made to a remote backup system, for example. Specific embodiments can reduce or eliminate loss of un-copied data by recognizing an imminent hazard of un-copied data loss caused by a disaster, for example. Specific embodiments can reduce or eliminate data loss, as well as reduce or eliminate possibility of inconsistent data sets in a system. Embodiments can comprise stand alone data storage units, methods and systems with multiple data storage media, for example. Further, embodiments can change priority of making local copies relative to making remote copies upon recognition of a probable occurrence of a hazardous event.